Expert guidance on prophylaxis and treatment of dermatologic adverse events with Tumor Treating Fields (TTFields) therapy in the thoracic region.

Tumor Treating Fields (TTFields) are electric fields, delivered via wearable arrays placed on or near the tumor site, that exert physical forces to disrupt cellular processes critical for cancer cell viability and tumor progression. As a first-in-class treatment, TTFields therapy is approved for use in newly diagnosed glioblastoma, recurrent glioblastoma, and pleural mesothelioma. Additionally, TTFields therapy is being investigated in non-small cell lung cancer (NSCLC), brain metastases from NSCLC, pancreatic cancer, ovarian cancer, hepatocellular carcinoma, and gastric adenocarcinoma. Because TTFields therapy is well tolerated and delivery is locoregional, there is low risk of additive systemic adverse events (AEs) when used with other cancer treatment modalities. The most common AE associated with TTFields therapy is mild-to-moderate skin events, which can be treated with topical agents and may be managed without significant treatment interruptions. Currently, there are no guidelines for oncologists regarding the management of TTFields therapy-related skin AEs in the thoracic region, applicable for patients with pleural mesothelioma or NSCLC. This publication aims to provide guidance on preventing, minimizing, and managing dermatologic AEs in the thoracic region to help improve patient quality of life and reduce treatment interruptions that may impact outcomes with TTFields therapy.

Calcium-sensing receptor signaling pathways in medullary thick ascending limb cells mediate COX-2-derived PGE2 production: functional significance.

We determined the functional implications of calcium-sensing receptor (CaR)-dependent, Gq- and Gi-coupled signaling cascades, which work in a coordinated manner to regulate activity of nuclear factor of activated T cells and tumor necrosis factor (TNF)-alpha gene transcription that cause expression of cyclooxygenase (COX)-2-derived prostaglandin E2 (PGE2) synthesis by rat medullary thick ascending limb cells (mTAL). Interruption of Gq, Gi, protein kinase C (PKC), or calcineurin (CaN) activities abolished CaR-mediated COX-2 expression and PGE2 synthesis. We tested the hypothesis that these pathways contribute to the effects of CaR activation on ion transport in mTAL cells. Ouabain-sensitive O2 consumption, an in vitro correlate of ion transport in the mTAL, was inhibited by approximately 70% in cells treated for 6 h with extracellular Ca2+ (1.2 mM), an effect prevented in mTAL cells transiently transfected with a dominant negative CaR overexpression construct (R796W), indicating that the effect was initiated by stimulation of the CaR. Pretreatment with the COX-2-selective inhibitor, NS-398 (1 microM), reversed CaR-activated decreases in ouabain-sensitive O2 consumption by approximately 60%, but did not alter basal levels of ouabain-sensitive O2 consumption. Similarly, inhibition of either Gq, Gi, PKC, or CaN, which are components of the mechanism associated with CaR-stimulated COX-2-derived PGE2 synthesis, reversed the inhibitory effects of CaR on O2 consumption without affecting basal O2 consumption. Our findings identified signaling elements required for CaR-mediated TNF production that are integral components regulating mTAL function via a mechanism involving COX-2 expression and PGE2 production.

CaR activation increases TNF production by mTAL cells via a Gi-dependent mechanism.

We evaluated the contribution of calcium-sensing receptor (CaR)-mediated G(i)-coupled signaling to TNF production in medullary thick ascending limb (mTAL) cells. A selective G(i) inhibitor, pertussis toxin (PTX), but not the inactive B-oligomer binding subunit, abolished CaR-mediated increases in TNF production. The inhibitory effect of PTX was partially reversed by using an adenylate cyclase inhibitor. CaR-mediated TNF production also was partially reversed by a cAMP analog, 8-Br-cAMP. IP(1) accumulation was CaR dependent and blocked by PI-PLC; partial inhibition also was observed with PTX. CaR increased calcineurin (CaN) activity by approximately threefold, and PTX prevented CaR-mediated increases in CaN activity, an nuclear factor of activated T cells (NFAT)-cis reporter construct, and a TNF promoter construct. The interaction between G(i) and PKC was determined, as we previously showed that CaR-mediated TNF production was CaN and NFAT- mediated and G(q) dependent. CaR activation increased PKC activity by twofold, an effect abolished by transient transfection with a dominant negative CaR construct, R796W, or pretreatment with PTX. Inhibition with the pan-specific PKC inhibitor GF 109203X (20 nM) abolished CaR-mediated increases in activity of CaN, an NFAT reporter, and a TNF promoter construct. Collectively, the data suggest that G(i)-coupled signaling contributes to NFAT-mediated TNF production in a CaN- and PKC-dependent manner and may be part of a CaR mechanism to regulate mTAL function. Moreover, concurrent G(q) and G(i) signaling is required for CaR-mediated TNF production in mTAL cells via a CaN/NFAT pathway that is PKC dependent. Understanding CaR-mediated signaling pathways that regulate TNF production in the mTAL is crucial to defining novel mechanisms that regulate extracellular fluid volume and salt balance.

NFAT regulates calcium-sensing receptor-mediated TNF production.

Because nuclear factor of activated T cells (NFAT) has been implicated in TNF production as well as osmoregulation and salt and water homeostasis, we addressed whether calcium-sensing receptor (CaR)-mediated TNF production in medullary thick ascending limb (mTAL) cells was NFAT dependent. TNF production in response to addition of extracellular Ca(2+) (1.2 mM) was abolished in mTAL cells transiently transfected with a dominant-negative CaR construct (R796W) or pretreated with the phosphatidylinositol phospholipase C (PI-PLC) inhibitor U-73122. Cyclosporine A (CsA), an inhibitor of the serine/threonine phosphatase calcineurin, and a peptide ligand, VIVIT, that selectively inhibits calcineurin-NFAT signaling, also prevented CaR-mediated TNF production. Increases in calcineurin activity in cells challenged with Ca(2+) were inhibited after pretreatment with U-73122 and CsA, suggesting that CaR activation increases calcineurin activity in a PI-PLC-dependent manner. Moreover, U-73122, CsA, and VIVIT inhibited CaR-dependent activity of an NFAT construct that drives expression of firefly luciferase in transiently transfected mTAL cells. Collectively, these data verify the role of calcineurin and NFAT in CaR-mediated TNF production by mTAL cells. Activation of the CaR also increased the binding of NFAT to a consensus oligonucleotide, an effect that was blocked by U-73122 and CsA, suggesting that a calcineurin- and NFAT-dependent pathway increases TNF production in mTAL cells. This mechanism likely regulates TNF gene transcription as U-73122, CsA, and VIVIT blocked CaR-dependent activity of a TNF promoter construct. Elucidating CaR-mediated signaling pathways that regulate TNF production in the mTAL will be crucial to understanding mechanisms that regulate extracellular fluid volume and salt balance.

Calcium-sensing receptor-mediated TNF production in medullary thick ascending limb cells.

Medullary thick ascending limb (mTAL) cells in primary culture express the Ca(2+)-sensing receptor (CaR), a G protein-coupled receptor that senses changes in extracellular Ca(2+) (Ca(o)(2+)) concentration, resulting in increases of intracellular Ca(2+) concentration and PKC activity. Exposure of mTAL cells to either Ca(o)(2+) or the CaR-selective agonist poly-L-arginine increased TNF-alpha synthesis. Moreover, the response to Ca(o)(2+) was enhanced in mTAL cells transfected with a CaR overexpression vector. Transfection of mTAL cells with a TNF promoter construct revealed an increase in reporter gene activity after exposure of the cells to Ca(o)(2+), suggesting that intracellular signaling pathways initiated by means of activation of a CaR contribute to TNF synthesis by a mechanism that involves transcription of the TNF gene. Neutralization of TNF activity with an anti-TNF antibody attenuated Ca(2+)-mediated increases in cyclooxygenase-2 (COX-2) protein expression and PGE(2) synthesis, suggesting that TNF exerts an autocrine effect in the mTAL, which contributes to COX-2-mediated PGE(2) production. Preincubation with the PKC inhibitor bisindolylmaleimide I inhibited Ca(2+)-mediated TNF production. Significant inhibition of COX-2 protein expression and PGE(2) synthesis also was observed when cells were challenged with Ca(o)(2+) in the presence of bisindolylmaleimide I. The data suggest that increases in TNF production subsequent to activation of the CaR may be the basis of an important renal mechanism that regulates salt and water excretion.